The present invention relates to improvements in a development station for an electrostatographic apparatus, such as a copier/duplicator, printer or the like.
Commonly-assigned U.S. Pat. No. 4,173,405, entitled "Developer Distribution Apparatus" which issued on Nov. 6, 1979 in the names of J. P. Swapceinski et al, discloses a development station for a two-component developer material. Developer material is driven in two opposite directions by a pair of augers that are adjacent to each other and have generally parallel axes. One of the augers rotates in a tube that has a series of openings of different sizes divided into groups so that material driven through the tube by the auger will be metered through the holes. The material flows into a sump and is delivered to a magnetic brush used for developing latent electrostatic images.
It is also known to provide a development station of electrostatographic apparatus with ribbon blenders for mixing and moving two-component developer material in a sump. One such station is disclosed in European Patent Publication No. 160,830, published Nov. 13, 1985, the disclosure of such publication being based on copending commonly-assigned U.S. Patent Application Serial No. 597,323, filed Apr. 6, 1984 in the names of B. J. Joseph and T. K. Hilbert. In the European patent publication coaxial inner and outer ribbon blenders drive developer material in two opposite directions when the ribbon blenders are rotated about a common axes. The European patent publication also discloses feeder vanes located on the radially outer ribbons of one of the ribbon blenders for picking up material from the sump and delivering it to a magnetic brush. As explained in the EPO publication, ribbon blenders have been found to be especially desirable for mixing and moving two-component developer materials wherein the carrier particles of such material comprise "hard" magnetic carrier particles.
Electrostatographic reproduction apparatus utilizing two-component developer materials for development of latent images tend to be relatively large and expensive. Also, they do not always have a positive developer flow path that will guarantee high image quality over long term periods. In addition, when the carrier particles of two-component developer materials comprise "hard" magnetic particles, special handling techniques are required, as explained in the before-mentioned EPO publication.